Libuše Hanková

Solvent impregnated resins: relation between impregnation process and polymer support morphology I. Di-(2-ethylhexyl)dithiophosphoric acid

Abstract The relationship between polymer support morphology and adsorption of di-(2-ethylhexyl)dithiophosphoric acid (DEHTPA) from alcoholic solution has been studied. As polymer supports investigated are the conventional commercial polymer adsorbents Amberlite XAD-2 and XAD-4 and two microporous polymer adsorbents prepared by post-polymerization crosslinking of swollen chloromethylated gel-type and macroreticular copolymers of styrene and divinylbenzene. Their morphology has been studied by nitrogen adsorption/desorption method. It was found that in the adsorption process DEHTPA fills the pore space gradually from the smallest pores up to pores with a diameter of approximately 10 nm.

Post-crosslinked polymer adsorbents and their properties for separation of furfural from aqueous solutions

Abstract Polymer adsorbents have been prepared by post-polymerization crosslinking of the swollen chloromethylated gel-type and macroreticular copolymers of styrene and divinylbenzene. Their morphology has been studied in the dry state by nitrogen adsorption/desorption method and in the swollen state by inverse steric exclusion chromatography. Their sorption properties were tested for the separation of furfural from aqueous solutions. Obtained data were compared with properties of conventional commercial polymer adsorbents Amberlite XAD-2 and XAD-4. At low concentrations of the sorbate in the surrounding solution the highly microporous post-crosslinked materials are much more efficient adsorbents than the conventional commercial polymers. However, their sorption capacity is restricted by limited pore volume and at higher equilibrium concentrations the high surface area macroporous polymers like Amberlite XAD-4 can be more efficient adsorbents.

Morphology of solvent-impregnated resins based on reactive supports

Hydrophobic metal-complexing extractants of the alkylphosphoric acid type (di-(2-ethylhexyl)dithiophosphoric acid, di-(2-ethylhexyl) monothiophosphoric acid and di-(2-ethylhexyl)phosphoric acid) are used as ligands for separation of metal ions from aqueous solutions. Upon immobilization on polymer carriers containing vinylpyridine and alkylamine basic groups they are held by chemisorption and absorbed into the polymer mass of the support. The capacity of the support for the organic ligand depends on the ability of its polymer mass to swell and also on the strength of the interaction between the basic functional groups of the polymer and the ligand. This is a newly observed phenomenon. Interaction of the supported ligand with metal ions results in expulsion of the ligand from the polymer mass. In macroreticular polymeric supports the metal-saturated ligand fills the macropores and escapes from the support when the macropore volume of the support is smaller than the volume of the organic ligand. Stripping of the metal from the ligand by washing with mineral acids causes the ligand to return from the macropores into the polymer mass of the support. Note: In this paper, the term ligand generally describes a hydrophobic metal extraction ligand.

Relations between morphology and catalytic activity of ion exchanger catalysts for synthesis of bisphenol A

Swollen-state morphology of a series of ion exchanger catalysts was analyzed by inverse steric exclusion chromatography. Correlation of the obtained information with data on activities of the catalysts for synthesis of bisphenol A (BPA) served for quantitative assessment of usefulness of various fractions of polymer mass of the examined ion exchangers for bisphenol A synthesis.